Modern pneumatic tires and in particular those intended for use on motor vehicles are subjected nowadays to ever increasing levels of stress under normal conditions of operation of such a vehicle. For that reason, there is often a requirement to subject a tire to testing operations to ensure inter alia that it can meet certain standards.
One process for testing a pneumatic tire such as a motor vehicle tire involves inflating the tire to be tested to a specified air pressure and then rolling the tire against a test surface such as a test drum or a pressure wheel, with the area of contact between the tire and the test surface constituting a tire contact patch. The forces and moments which act at the tire contact patch can thus be measured. The measured forces and moments may for example provide information about the uniformity of the tire, as referred to for example in `Werkstatt und Betrieb`, 31st year, Issue No. 3, pages 183-188. In addition, in particular in order to test the operational reliability of a tire, it is possible to simulate various combinations of loadings and tests in respect of operational strength can be carried out under different accumulations of loadings, by presetting certain test parameters for carrying out the testing procedure. The required measurements may be attained by means of measuring hub assemblies (reference may be made in this respect to Hofmann News 4).
Before it is possible to begin the actual measuring procedure, it may be necessary in at least some cases to ensure that the tire is properly warmed up and has thus reached a temperature which at least approximately corresponds to its normal operating temperature. That is intended to ensure that the tire is operated in the test procedure under conditions which are close to those involved in a practical context, while possibly also providing that the measuring apparatus is at the appropriate temperature to provide for the properly established characteristics thereof in regard to temperature, for example when using a measuring hub assembly with strain gauges, which is disposed at the axis of the tire for supporting same during the test run. To achieve that aim, the tire may be heated up by rolling it against the test surface, thus simulating the situation where a tire is fitted in a practical context to a motor vehicle and rolls against the road surface when the vehicle begins to move. At the end of that heating time, the actual operation of measuring the forces and moments involved during the test run can then be dealt with. The heating time may be up to for example around two minutes, depending on the speed of tire rotation involved. It will be appreciated however that heating up the tire in that way means that the total testing time during which the tire to be tested is in the tire testing machine is considerably increased. In addition, it has not been possible hitherto to provide for properly controlled heating of the tire in that way.
On the other hand however, at high speeds of rotation, during a measuring run, the tire may be subjected to an excessively strong heating effect, in particular when carrying out high-speed testing in regard to establishing the operational reliability of a pneumatic tire.